Fabrics made of fibers having square cross section

ABSTRACT

Fibers of square cross sections are presented in the invention. The square fiber leads to higher packing density and results in higher wind resistance in fabrics as compared to the conventional round fibers and other polygonal fibers. Therefore, the square fiber is more suitable for manufacture of the windproof clothing. In addition, the square fibers exhibit higher luster than the round fibers and other polygonal fibers due to the flat and shiny fiber surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of application Ser. No.10/282,083, filed Oct. 29, 2002, which claims the benefit of TaiwaneseApplication No. 90126697, filed Oct. 29, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of fabricating non-hollowfibers having regular polygonal cross-sections. In particular, thepresent invention relates to a method of fabricating a non-hollow fibershaving a square cross-section with approximately equilateral sides. Thepresent invention also relates to fabrics manufactured by the fibers,which demonstrate superior brightness, and windproof characteristics.

2. Description of the Related Art

Many efforts have been made to improve the characteristics of syntheticfilaments or fibers so as to impart fabrics or textiles with enhancedperformance and functions, such as moisture transport, thermalinsulation, air permeability, antistatic, sustained release,antibacterial, and windproof properties.

U.S. Pat. No. 5,057,368 issued to Largman et al, disclosed trilobal orquardrilobal filaments for use in various applications such asfiltration, insulation, moisture transport and others.

U.S. Pat. No. 5,279,879 issued to Goodall et al, disclosed a hollowsynthetic filament having a four sided cross-section and foursubstantially evenly spaced continuous holes. The filament is suitablefor making thermal wear and carpets which require extra thermalinsulation or bulkiness.

High density fabrics in which yarns are woven in a compact manner aremore desirable for windproof wears. Such clothes are conventionally madeof ultra-fine round filaments to reduce interfiber spaces and to achievehigh fabric density. The present invention discovers that fibers ofsquare cross section lead to even less interfiber spaces as compared tothe conventional fine round filaments.

SUMMARY OF THE INVENTION

The primary objective of the present invention is therefore to providefabrics or textiles that demonstrate superior windproof (i.e., lower airpermeability) characteristics and can be made at a lower cost.

To attain the objective, the invention provides non-hollow fibers havingsquare cross-section where each side has approximately equal length. Thesquare fibers can be arranged in a denser manner, which has reducedinterfiber spaces, when woven and finished properly. Therefore, theresultant fabrics or clothes possess superior windproof characteristics.

Another advantage of this invention is that the dense fabrics made ofthe square fiber may impart superior thermal insulation due to reductionof air flow and thus heat loss by convection.

A third unique attribute of this invention is that the fabrics made ofthe square fibers are more lustrous than conventional fabrics due to theflatter surface, which in turn is the result of the flat surface of thesquare cross section. The superior luster of the fabrics renders thedesigner an additional dimension in fashion design.

The fibers or filaments of the present invention are made by using aspinneret orifice having a contoured quasi-polygonal cross-section.

Specifically, the fibers or filaments of the invention are made bymelting a thermoplastic polymer; extruding the melted polymer through aspinneret orifice having a contoured quasi-square cross-section to formmolten filaments; and solidifying the molten filaments. The solidifiedfilaments are subsequently drawn to achieve desired properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description in conjunction with the examples andreferences made to the accompanying drawing, wherein:

FIG. 1 is a photo showing the cross-section of the square fibers made inExample 1.

FIG. 2 is a photo showing the cross-section of the triangular fibersmade in Example 3.

DETAILED DESCRIPTION OF THE INVENTION

The fibers or filaments of the invention are non-hollow fibers andfilaments having square cross-section.

The term “square” indicates that each side of the tetrahedral polygonhas approximately equal length. It is noted, however, each side ofsquare may have a variation less than 50%, preferably less than 5%, fromthe mean value

The filaments are prepared by spinning molten polymer through spinneretcapillaries or orifices designed to provide the desired configuration ofthe cross-section of the filaments. That is, the orifices are designedand formed in a configuration having a corresponding contoured polygonalcross-section.

The filaments may be prepared from synthetic thermoplastic polymers.Examples of these polymers include but are not limited to polyester,polyamide and polyolefin.

Polyesters that are suitable for use in this invention are those derivedfrom the condensation of aromatic and cycloaliphatic dicarboxylic acidsand may be cycloaliphatic, aliphatic or aromatic polyesters. Examples orthese polyesters are poly(ethylene terephthalate), poly(proyleneterephthalate), poly(cyclohexylenedimethylene terephthalate),poly(lactide), poly(butylene terephthalate), poly(glycolic acid) andpoly(ethylene adipate). Among these, poly(ethylene terephthalate) ismost frequently used. Other examples of suitable polyesters are thosementioned in U.S. Pat. Nos. 4,454,196, 4,410,073 and 4,359,557incorporated herein for references.

Polyamides of the above description are well known in this art andinclude, for example nylon 6 (poly(6-aminohexanoic acid)), nylon 66(poly(hexamethyleneadipamide)), nylon 4 (poly(4-aminobutyric acid)),nylon 11 (poly(11-amino-undecanoic acid) and the like. The preferredpolyamides are nylon 6 and nylon 66. Other examples of suitablepolyamides can be seen from “Textile Fiber Handbook”, 5th edition,Trowbridge GB (1984), pp 19-20.

Examples of polyolefin that can be used in this invention as rawmaterial include, but are not limited to polyethylene, polypropylene,polyisobutene, poly(4-methyl-1-pentene), poly(3-methyl-1-butene), andpoly(1-hexene). Among these polyolefins, polypropylene is the mostcommonly used. Other examples of useful polyolefins can be found fromU.S. Pat. Nos. 4,137,391, 4,562,869, 4,567,092 and 4,559,862 includedherein for reference. Also, a blend of the above-mentioned polymers isalso suitable for use according to the present invention.

The manufacturing method of the fibers or filaments of the invention aresubstantially the same as conventional melt spinning techniques exceptthat a spinneret orifice having a configuration sufficient to provide afiber having regular polygonal cross-section is used. The raw material,i.e., the thermoplastic polymer, is melted and is extruded through thespinneret to form molten filaments. The spinning temperature is usuallyset between 150-300° C., depending on the melting point of the polymerand the type of the spinneret. For example, if polyethyleneterephthalate is used as raw material, it is heated to 270-300° C. tomelt the polymer. However, if polypropylene is employed, the spinningtemperature is preferably set in the range of 200-280° C.

In the melt spinning process, the molten polymer is extruded into air orother gases, or into a suitable liquid to quench and solidify the moltenfilaments. The solidification process is conducted by using quenchinggas, usually cooling air, at a temperature of about 10-25° C. Thesetting of the temperature and the velocity of the quenching air blownto the molten filaments depend on the polymer and the filamentproperties desired. The filaments may be lubricated with oil at about100-120 cm below the spinneret to facilitate solidification. The amountof oil (OPU, oil per unit) applied is about 0.5-0.8% and may varydepending on the polymer used and spinning conditions. Before beingtaken up, the filaments may be subjected to further processing such asdrawing or texturing to achieve desired properties.

The fibers or filaments produced by the above process have a regularpolygonal cross-section, in which all sides are of approximately equallength. Preferably, variation of each side of the polygonalcross-section of the fabricated fiber is less than 50%, more preferablyless than 5% from the mean value. The fibers of the invention can beemployed in many applications, and are not limited to the fabrication ofwoven, non-woven, and knitted fabrics or clothes. The fibers of theinvention are particularly suited for use in the fabrication of fabricsor textiles that require superior wind resistance, luster, and thermalinsulation.

The following examples are presented to further illustrate the inventionand are not to be construed as limitations thereon.

EXAMPLE 1 The Preparation of PET Fiber Having Square Cross-section (1)

A melt dope was prepared by melting regular polyester resin (R-PET) ofintrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic FibersCo. Taiwan) at 285° C. The melt was then spun at 42.7 grams/minutethrough a spinneret having 48 contoured quasi-square orifices. Thefilaments extruded from the spinneret were then cooled by blowing with aquenching air of 16° C. at a velocity of 0.55 m/sec. After quenching,the filaments were treated with an aqueous liquid containing 10% oil bycontacting an applicator located at a distance of 110 cm below thespinneret to facilitate the solidification of the hot filaments. Theamount of oil applied onto the fiber was 0.83% of the fiber weight. Thecooled and solidified filaments were then passed through a set of driventake-up rolls and winded up at a speed of 3200 meter/minute to obtain apartially oriented yarn (POY). The obtained yarn bundles have 48filaments and 120 deniers in linear density. The partially oriented yarnis further drawn to become fully oriented yarn (FOY). The FOY bundleshave 48 filaments and 75 deniers in linear density. The properties ofPOY and FOY yarns are summarized in Table 1. The cross-section of theresultant fiber is shown in FIG. 1.

EXAMPLE 2 The Preparation of PET Fiber Having Square Cross-section (2)

A melt dope was prepared by melting regular polyester resin (R-PET) ofintrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic FibersCo. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minutethrough a spinneret having contoured quasi-square orifice. The filamentsextruded from the spinneret were then cooled by blowing with a quenchingair of 16° C. at a velocity of 0.45 meter/sec. After quenching, thefilaments were treated with an aqueous liquid containing 10% oil bycontacting an applicator located at a distance of 110 cm below thespinneret to facilitate the solidification of the hot filaments. Theamount of oil applied onto the fiber was 0.81% of the fiber weight. Thecooled and solidified filaments were then passed through a set of driventake-up rolls and winded up at a speed of 3200 meter/minute to obtain apartially oriented yarn (POY). The obtained yarn bundles have 48filaments and 80 deniers in linear density. The partially oriented yarnis further drawn to become fully oriented yarn (FOY). The FOY bundleshave 48 filaments and 50 deniers in linear density. The properties ofPOY and FOY yarns are summarized in Table 1 below.

COMPARATIVE EXAMPLE 1 The Preparation of PET Fiber Having RoundCross-section (1)

A melt dope was prepared by melting regular polyester resin (R-PET) ofintrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic FibersCo. Taiwan) at 285° C. The melt was then spun at 42.7 grams/minutethrough a spinneret with 48 round orifices. The filaments extruded fromthe spinneret were then cooled by blowing with a quenching air of 16° C.at a velocity of 0.55 meter/sec. After quenching, the filaments weretreated with an aqueous liquid containing 10% oil by contacting anapplicator located at a distance of 110 cm below the spinneret tofacilitate the solidification of the hot filaments. The amount of oilapplied onto the fiber was 0.83% of the fiber weight. The cooled andsolidified filaments were then passed through a set of driven take-uprolls and winded up at a speed of 3200 meter/minute to obtain apartially oriented yarn (POY). The obtained yarn bundles have 48filaments and 120 deniers in linear density. The partially oriented yarnis further drawn to become fully oriented yarn (FOY). The FOY bundleshave 48 filaments and 75 deniers in linear density. The properties ofPOY and FOY yarns are summarized in Table 1.

COMPARATIVE EXAMPLE 2 The Preparation of PET Fiber Having RoundCross-section (2)

A melt dope was prepared by melting regular polyester resin (R-PET) ofintrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic FibersCo. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minutethrough a spinneret with 48 round orifices. The filaments extruded fromthe spinneret were then cooled by blowing with a quenching air of 16° C.at a velocity of 0.45 meter/sec. After quenching, the filaments weretreated with an aqueous liquid containing 10% oil by contacting anapplicator located at a distance of 110 cm below the spinneret tofacilitate the solidification of the hot filaments. The amount of oilapplied onto the fiber was 0.81% of the fiber weight. The cooled andsolidified filaments were then passed through a set of driven take-uprolls and winded up at a speed of 3200 meter/minute to obtain apartially oriented yarn (POY). The obtained yarn bundles have 48filaments and 80 deniers in linear density. The partially oriented yarnis further drawn to become fully oriented yarn (FOY). The FOY bundleshave 48 filaments and 50 deniers in linear density. The properties ofPOY and FOY yarns are summarized in Table 1. TABLE 1 Before drawingAfter drawing Linear Tenacity Elongation Linear Tenacity Elongationdensity (g/d) (%) density (g/d) (%) Example (1) 120 d 2.64 123 75 d 4.7934.5 square Example (2) 80 d 2.53 121 50 d 4.57 32.1 square Comp. Exam.120 d 2.72 120 75 d 4.86 32.3 (1) round Comp. Exam. 80 d 2.65 118 50 d4.65 30.2 (2) roundNote:d: denier

EXAMPLE 3 The Preparation of PET Fiber with Regular TriangularCross-section

A melt dope was prepared by melting regular polyester resin (R-PET) ofintrinsic viscosity of 0.64 (manufactured by Shinkong Synthetic FibersCo. Taiwan) at 285° C. The melt was then spun at 28.4 grams/minutethrough a spinneret with 48 round orifices. The filaments extruded fromthe spinneret were then cooled by blowing with a quenching air of 16° C.at a velocity of 0.45 meter/sec. After quenching, the filaments weretreated with an aqueous liquid containing 10% oil by contacting anapplicator located at a distance of 110 cm below the spinneret tofacilitate the solidification of the hot filaments. The amount of oilapplied onto the fiber was 0.82% of the fiber weight. The cooled andsolidified filaments were then passed through a set of driven take-uprolls and winded up at a speed of 3200 meter/minute to obtain apartially oriented yarn (POY). The obtained yarn bundles have 48filaments and 80 deniers in linear density. The partially oriented yarnis further drawn to become fully oriented yarn (FOY). The FOY bundleshave 48 filaments and 50 deniers in linear density. The cross-section ofthe resultant fiber is shown in FIG. 2.

One of the unique characteristics of the fibers with equilateralpolygonal cross section is related to stacking of the fiber. As shown inTable 2, in the case of the equilateral polygonal fiber, the windresistance of the fabric, in terms of pressure drop at a certain airflux, is significantly higher than the fabrics made of conventionalround fibers. Especially, the wind resistance of the fabric of squarefiber is much higher than the fabrics made of triangular fibers. Athigher air fluxes, the trends are the same with slightly differentratios. In some embodiments, the fabric of square fibers may have a windresistance of more than 3 times higher than a fabric made of roundfibers, and more than 50% higher than that of triangular fibers.

It is surprising and unexpected that the square fiber results inremarkably higher wind resistance in fabrics as compared to triangularfiber, since it was originally held that the square fiber and triangularfiber would have the same packing behavior due to their flat surfaces.TABLE 2 Comparison of wind resistance of PET woven fabrics Air fluxSquare fiber Triangular Round fiber (l/min) (mm H₂O) fiber (mm H₂O) (mmH₂O) 20 37 24 11 40 96 59 23 60 136 88 39 80 148 104 59 100 150 122 93Remarks□fiber spec: 50 d/48 f; fabric structure□1/1 plain weave, weft200 threads/inch, warp 110 threads/inch.

The luster, measured as the percentage of the light reflection from thefabric surface, is also shown in Table 3. Fabrics of both square andtriangular fibers show higher luster than that of the round fiber. Thisis due to the light reflection from the flat surface of either thesquare or the triangular fiber. The fabric of square surface has thehighest luster because of the better fiber stacking on the fabricsurface, which results in a flatter and shinier surface. Specially, thefabric of square fibers has a luster of more than 2 times higher thanthat of round fibers, and surprisingly, more than 50% higher than thatof triangular fibers. TABLE 3 Comparison of air permeability and lusterof PET woven fabrics Pressure Square fiber Triangular fiber Round fiber(Pa) Air permeability (cc/cm²□ sec) 25 0.132 0.160 0.188 50 0.169 0.2240.279 75 0.198 0.336 0.474 100 0.240 0.520 0.660 125 0.276 0.575 0.773150 0.331 0.691 0.850 Luster (%) 5.78 3.24 2.56Remarks□(1) Fiber spec.: 50 d/48 f; fabric structure□ 1/1 plain weave,weft 200 threads/inch, warp 110 threads/inch.(2) Luster is measured in terms of light reflection from the fabrics.All fabrics are not colored.

While the invention has been described by way of examples and in termsof the preferred embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A fabric of high wind resistance, made of melt-spinning fibers having square cross-section, wherein each side of the square cross-section has approximately equal length.
 2. The fabric as claimed in claim 1, wherein variation of each side of the polygonal cross-section of the fibers is less than 50% from the mean value.
 3. The fabric as claimed in claim 2, wherein variation of each side of the polygonal cross-section of the fibers is less than 5% from the mean value.
 4. The fabric as claimed in claim 1, in the form of woven fabric, knitted fabric or non-woven fabric.
 5. The fabric as claimed in claim 1, having a wind resistance higher than a fabric made of round fibers.
 6. The fabric as claimed in claim 5, having a wind resistance of more than 3 times higher than a fabric made of round fibers.
 7. The fabric as claimed in claim 1, having a luster higher than a fabric made of round fibers.
 8. The fabric as claimed in claim 7, having a luster of more than 2 times higher than a fabric made of round fibers.
 9. The fabric as claimed in claim 1, having a wind resistance higher than a fabric made of triangular fibers.
 10. The fabric as claimed in claim 9, having a wind resistance of more than 50% higher than a fabric made of triangular fibers.
 11. The fabric as claimed in claim 1, having a luster higher than a fabric made of triangular fibers.
 12. The fabric as claimed in claim 11, having a luster of more than 50% higher than a fabric made of triangular fibers.
 13. The fabric as claimed in claim 1, wherein the fiber is formed of a material selected from the group consisting of polyester, polyamide and polyolefin.
 14. The fabric as claimed in claim 13, wherein the polyester comprises poly(ethylene terephthalate), poly(proylene terephthalate), poly(cyclohexylenedimethylene terephthalate), poly(lactide), poly(butylene terephthalate), poly(glycolic acid), or poly(ethylene adipate).
 15. The fabric as claimed in claim 13, wherein the polyamide comprises nylon 6 (poly(6-aminohexanoic acid)), nylon 66 (poly(hexamethyleneadipamide)), nylon 4 (poly(4-aminobutyric acid)), nylon 11 (poly(1l-amino-undecanoic acid).
 16. The fabric as claimed in claim 13, wherein the polyolefin comprises polyethylene, polypropylene, polyisobutene, poly(4-methyl-1-pentene), poly(3-methyl-1-butene), or poly(1-hexene). 